ANNUAL REPORT - Inter-American Tropical Tuna Commission · 2018-06-27 · ANNUAL REPORT OF THE INTER-AMERICAN TROPICAL TUNA COMMISSION, 1997. INTRODUCTION. The Inter-American Tropical1\ma

ANNUAL REPORT of the

Inter-American Tropical Tuna Commission

1997

INFORME ANUAL dela

Comisi6n Interamericana del Atlin Tropical

La Jolla, California 1999

CONTENTS-INDICE ENGLISH VERSION-VERSION EN INGLES

Page INTRODUCTION 7 COMMISSION MEETINGS 8 ADMINISTRATION 14

Budget 14 Financial statement 14

INTER-AGENCY COOPERATION 14 FIELD STATIONS 17 PUBLICATIONS 17 TUNA-BILLFISH PROGRAM 18

The fishery 18 Yellowfin quotas 22 Research 23 Status of the tuna and swordfish stocks in 1997 and outlook for 1998 35

TUNA-DOLPHIN PROGRAM 73 Data collection 74 Gear program 74 Research 75 The International Dolphin ConselVation Program 78

FIGURES-FIGURAS 79

TABLES-TABLAS 151

VERSION EN ESPANOL-SPANISH VERSION Pagina

INTRODUCCION 201 REUNIONES DE LA COMISION

Condici6n de los stocks de atlmes y peces espada en 1997 y perspectivas

202 ADMINISTRACION 208

Prepuesto 208 Informe financiero 208

COLABORACION ENTRE ENTIDADES AFINES 208 OFICINAS REGIONALES 211 PUBLICACIONES 211 PROGRA.t\1 ATUN-PICUDO 212

La pesqueria 212 Cuotas de aleta amarilla 217 La investigaci6n 217

para 1998 230 PROGRAMA ATUN-DELFIN 271

Toma de datos 271 Programa de artes de pesca 272 La investigaci6n 273 Progranm Intemacional para la Conservacion de Delfines 276

APPENDIX l-ANEXO 1 STAFF--PERSONAL 277

APPENDIX 2-ANEXO 2 AGREEMENT FOR THE CONSERVATION OF DOLPHINS--ACUERDO PARA LA CONSERVACION DE DELFINES 280

APPENDIX 3-ANEXO 3 STATEMENT BY MEXICO AT THE 33RD INTERGOVERNMENTAL MEETING--DECLARCION DE MEXICO A LA 33a REUNION INTERGUBERNAMENTAL 291

APPENDIX 4--ANEXO 4 INTERNATIONAL REVIEW PANEL, RULES OF PROCEDURE--PANEL INTERNACIONAL DE REv1SION, REGLAS DE PROCEDIMIENTO 295

APPENDIX 5-ANEXO 5 CONSENSUS OF SANTA IVrARTA--CONSENSO DE SANTA MARTA 302

APPENDIX 6-ANEXO 6 RESOLUTION OF SANTA MARTA--RESOLUCION DE SANTA MARTA 304

APPENDIX 7-ANEXO 7 FINANCIAL STATEMENT--DECLARACION FINANCIERA 305

APPENDIX 8--ANEXO 8 CONTRIBUTIONS BY lAITC STAFF MEMBERS PUBLISHED DURING 1997--CONTRIBUCIONES POR PERSONAL DE ClAT PUBLICADOS DURANTE 1997 310

COMMISSIONERS OF THE INTER-AMERICAN TROPICAL TUNA COMMISSION AND THEIR PERIODS OF SER\1CE FROM ITS

INCEPTION IN 1950 UNTIL DECEMBER 31, 1997

LOS COMISIONADOS DE LA COMISION INTERAMERICANA DEL ATUN TROPICAL YSUS PERIODOS DE SERVICIO DESDE LA FUNDACION

EN 1950 HASTA EL 31 DE DICIEMBRE DE 1997

COSTA RICA

VirgilioAguiluz . . . 1950-1965 Jose L. Cardona-Cooper 1950-1979 Victor Nigro . . . . .. . . . .. .. . . . .. . .. .. 1950-1969 Fernando Flores B. Milton H. LOpez G. Eduardo Beeche T. Francisco Tenin Valls Manuel Freer . . . . . . . . . . . . . Gabriela Myers Rodolfo Saenz o. Manuel Freer Jimenez. . . Carlos P. Vargas Stewart Heigold Stuart Herbert Nanne Echandi. Jaime Basadre Oreamuno Luis Pro1S Chaveni . . . . . . . . .. Alvaro Moreno Gomez 1994-1996

UNITED STATES OF AMERICA

Eugene D. Bennett _., 1950-19681

. 1958-1977

. , 1965-1977 . 1969-1971 . . . .. 1971-1977

. 1977-1979 . .. 1977-1979

. , 1977-1979 . . .. 1989-1990

1989-1990 1990

. , 1990-1994 , 1994

1994-1P97

Milton C. James. . .. . . . . .. . . .. .. . Lee F. Payne Gordon W. Sloan John L. Kask John L. Farley Arnie J. Suomelal . Robert L. Jones . J. Laurence McHugh . . . . .. John G. Driscoll, Jr. . . . . . . . . .. , 1962-19754 William H. Holmstrom. . . .. Donald P. Loker William M. Terry Robert C. Macdonald Steven E. Schanes Wilvan G. Van Campen Jack Gorby , Glen H. Copeland Wyrnberley CoelT Henry R. Beasley . .. . . . . . .. . . . . .. Mary L. Walker Jack Bowland . .. . .. Bro'bara H. Britten. . . M. Austin Foooan . . James T. McCarthy Michael F. Tillman . .

PANAMA

Miguel A. Corro Domingo A. Diaz

1950-1951 , 1950-19612 , 1951-1957

1952 1953-1956

, 1957-1959 1958-19653 1960-1970

Walter Myers, Jr. . . . .. Richard Eisenmailll . . . , 1958-1960 Gabriel Galindo ..... .. . .. . . . 1958-1960 Juan L. de Obarrio . . . . . . . . . 1958-1980 Harmodio Arias, Jr. . . .. 1961-1962 Roberto Novey. . .. . . . . . . .. . . . . . . .. 1961-1962 Carlos A. Lopez Guevara 1962-1974 Dora de Lanzner 1963-1972 CroMo Quintero . 1963-1972 Arquimedes Franqueza . . . . . 1972-1974 Federico Humbert, Jr. 1972-1974

1966-1973 , 1969-1976

1970-19735 1973-1994

, 1973-1974 1974-1976 1975-1992

, 1976-1977 1977-1988 1986-1994

. 1988-1994 1992

, 1994.. 1994.. 1994. 1994

1953-1957 1953-1957 1953-1957

Carolina T. de Mouritzen . . .. 1974-1985 Jaime Valdez .. 1974-1985 Carlos Arellano 1. .. 1980-1983 Luis E. Rodriguez 1980-1984 Arnlando Martinez Valdes. . . . . . . . . . .. 1984-1988 Carlos E. lcaza E. 1985-1988 Dalva H. Arosemena M. 1988-1990 Jesus A. Correa G. . . . . . . . . . . . . . . . . .. 1989-1994 Jorge Lyrnberopulos 1989 Roy E. Cardoze 1990-1994 Carlos E. lcaza E. . 1990-1991 Jose Antonio lcaza 1990-1991 Jorge Lyrnberopulos 1991-1994 Juan Antonio Varela 1991-1994 Jose Donoso 1994-1995 Ricardo A. Martans .. . . . . . . . . . . . . . .. 1994-1997 Jose A. Troyano 1994-1997 Arnlando Martinez Valdes. . . . . . . . . . .. 1995-1997

ECUADOR

Pedro Jose Arteta 1961-1962 Eduardo Burneo 1961-1965 Enrique Ponce y Cabro . . . . .. 1961-1963 Cesar Raza . .. .. .. .. . .. .. 1961-1962 Frallcisco Baquerizo 1963 Hector A. Chiriboga 1963-1966 Vicente Tamro1z A. 1964-1965 Luis Pareja P. .. . .. . . . . .. . . . . . 1966-1968 Vinicio Reyes E 1966-1968 Wilson Vela H. 1966-1968

MEXICO

Mauro Cardenas F. .. 1964-1968 Hector Chapa Saldai'ia. . . . . . . . . . . . . .. 1964-1968 Rodolfo Ramirez G _1964-1966 Maria Emilia Tellez B. . __ . . .. 1964-1971 Juan Luis Cifuentes 1. . . . . . . . . . . . . . .. 1967-1970 Alejandro Celv3ntes D 1968-1978 Aruin Zarur M. 1968-1970 Arturo Diaz R. 197()"1978 Joaquin Mercado F. . . . . . . . . . . . . . . . .. 197()..1977 Pedro Mercado S. .. '" 197()"1975 Fernando Castro y Castro 1975-1977

CANADA

Emerson Gennis . .. 1968-1969 Alfred W. H. Needler . .. . . . . .. . . . . . .. 1968-1972 E. Blyth young 196R-19RO Leo E. Labrosse . . . . . . . . . . . 1970-1972 Robert L. Payne. . .. . .. . . . . .. . .. . . .. 1970-1974 S. Noel Tibbo 1070-1977 G. Ernest Waring . .. . .. . . .. .. . . . . . .. 1970-1976 James S. Beckett 1977-1984 Michael Hunter . 1981-1984

JAPAN

Shoichi Masuda. .. .. 1971-1985 Tomonari Matsushita 1971-1973 Fumihiko Suzuki 1971-1972 Seiya Nishida. .. . { . . 1972-1974 Kunio Yonezawa 1973-1979

• • • • • ••

Harunori Kaya 1974-1976 Deceased in service December 18, 1968 Michio Mizoguchi 1976-1977 Murin en servicio activo eI 18 de diciembre de 1968 Michihiko Junihiro 1979-1980 Deceased in service April 10, 19610 •••••••••••• 0 • " Tatsuo Saito. .. . . . .. . . . . .. . . . . . .... 1979-1983 Millin en servicio activo eI 10 de abriI de 1961 Toshio Isogai ..... 0 1980-1983 Deceased in service April 26, 1965 Susumu Akiyama .. 0 1984-1986 Mmi6 en sen'icio activo el 26 de abril de 1965•••••••••••• 0 • •• Ryuichi Tanabe 1984-1985 Deceased in sen1ce October 16, 19750 0 .. • •• Satoshi Moriya 1985-1987 Mun6 en sen1cio activo e116 de octubre de 19750 0 • •• Yamato Ueda 1985- Deceased in service May 5, 19730 0 0 Takehisa Nogami 1986-1989 Muri6 en semcio activo el 5de mayo de 1973 Kazuo Shima 1987-19890 Kouji Imamura " 1989-1992 Shigenobu Kato . 0 1989-19910 0 Koichiro Seki 1991-1994 Masahiro Ishikawa 1992-19940 •••••••••• Kenro lino 0....................... 1994-1995 Minoru Morimoto .... 0 1994-19970 • 0 • .. • • .. • •• Yasuo Takase 19960 • • • • • • • • • •• !chiro Nomura. . . .... 1997

FRANCE

Serge Garache .. 0 1973-19830 • .. • .. Robert Letaconnaux 197:1-198:10 • • • • • 0 0 Rene Thibaudau 1976-19770 Maurice Fourneyron " 1980-1987 Dominique Piney o. 1984-19890 Daniel Silvestre 1990-1991 Jean Fran~ois Gilon .. 0 1992• • • • • • • 0 • " Patrice Corler .,. 0 19930 • • •• Phillipe Peronne 1994Jean-Paul Rivalld . , , ' ••• 1994-19950 0 David Portal 1996-19970 ••• , 0 • • •• Sebastien Surun ,.. 1997

NICARAGUA

Gilberta Bergman Padilla ' .. , ... , . . .. 1973-1977 Antonio Flores Arana '" 0 0 , • 0 1973-1976•• 0 0 ' •• Jose B. Godoy M. .. . . . . . .. . . . . .. . . .. 1976-1980 Octavio GUtielTeZ D. . 1977-19800 ••••• Silvio Campos M 1977-1980 Janti1 Urroz Eo 1977-19850 0 0 Abelino Ar6stegui Valladares 1985-1988 Sergio Martinez Casco ,... 1988

VANUATU

Richard Carpenter 1991-19940 ••• Darosday Kenneth 1991-19950 ••••••••••• Julian Ala 19950 • 0 • • • .. • • • .. • • .. • • .. • • ••

VENEZUELA

Francisco Herrera renin o 1992-199400 ••• Carlos Gimenez 1994-19960 " Roberto Oltisi 1994-1997 Jean-FranGois Pulvenis 19940 •••• Alfredo Zuloaga 1994-19950 Miriam R. de De Venanzi , . .. 1995-1996 Hugo Alsina Lagos 19950 Mmia Estela Bermudez. , . . . . . . . . . . .. 1996

ELSALVADOR

ANNUAL REPORT OF THE INTER-AMERICAN TROPICAL TUNA COMMISSION, 1997

INTRODUCTION

The Inter-American Tropical1\ma Commission (IATTC) operates under the authority and direction ofa convention originally entered into by Costa Rica and the United States. The convention, which came into force in 1950, is open to adherence by other govemments whose nationals fish for tropical tuna,> and tuna-like species in the eastern Pacific Ocean (EPO). Under this provision Panama adhered in 1953, Ecuador in 1961, Mexico in 1964, Canada in 1968, Japan in 1970, France and Nicaragua in 1973, Vanuatu in 1990, Venezuela in 1992, and EI Salvador in 1997. Mexico withdrew from the IATTC in 1978 and Canada in 1984.

The li\TTC fulfills its responsibilities with two programs, the Tuna-Billfish Program and the TunaDolphin Program. The principal responsibilities of the Tuna-Billfish Program are (1) to study the biology of the tunas and tuna-like species of the EPO to estimate the effects that fishing and natural factors have on their abtmdance and (2) to recommend appropriate conservation measures so that the stocks of fish can be maintained at levels which will afford maximum sustainable catches. The principal responsibilities of the Tuna-Dolphin Program are (1) to monitor the abundance of dolphins and their mortality incidental to fishing through the collection of data aboard tuna purse seiners fishing in the EPO, (2) to analyze these data and make appropriate recommendations for the conservation of dolphins, (3) to study the causes of mortality of dolphins during fishing operations and encourage fishermen to adopt fishing teclmiques which minimize the mortalities of dolphins, and (4) to study the effects of different modes of fishing on the vm10us fish and other animals of the pelagic ecosystem.

To carry out these missions, the IATTC conducts a wide variety of investigations at sea, in ports where tunas are landed, and in its laboratories. The research is calTicd out by a pennanent, internationally-recruited research and support staff (Appendix 1) selected by the Director, who is directly responsible to the Commission.

The scientific progran1 is now in its 47th year. The results of the IATTC staff's research are published in the IATTC's Bulletin series in English and Spanish, its two official languages, in its Special Report and Date Report series, and in books, outside scientific journals, and trade journals. Reviews of each year's operations and activities are reported upon in the IATTC's Annual Reports, also in the two languages.

8 TUNA COMMISSION

COMMISSION MEETINGS

The convention of the IATTC requires that it meet at least once each year. In addition, intergovernmental meetings (IGMs), involving representatives of member governments and non-member governments which are interested in the fisheries for tropical tunas in the eastern Pacific Ocean (EPO), are nearly always held in conjunction with the IATTC meetings. Two permanent working groups, the International Review Panel (IRP) and the Scientific Advisory Board (SAB), were established by the Agreement for the Conservation of Dolphins adopted at the 24th IGM, held in June 1992. (The latest version of that agreement is reproduced as Appendix 2 of this report.) In 1997 an ad hoc Bigeye Management Options Working Group was established. The proceedings of the meetings of these groups held in 1997 are slllnmarized in this section.

58TH MEETING OF THE IATTC

The 58th meeting of the IATTC was held in San Jose, Costa Rica, on June 3-4, 1997. Dr. Jorge Canlpos M. of Costa Rica served as Chairman. Representatives of the member governments of Costa Rica, France, Japan, Panama, the United States, and Venezuela attended, as did observers from Colombia, Ecuador, EI Salvador, MeXico, the Republic of China, Spain, the Commission for the Conservation of Southern Bluefin Tuna, the International Whaling Commission, the Fundaci6n para la Defensa de la Naturaleza (FUDENA), Greenpeace International, and the Humane Society International.

The following agenda was adopted: 1. Opening of the meeting 2. Adoption of agenda 3. Review of current tuna research 4. The 1996 fishing year 5. Status of tuna stocks 6. Review of tuna-dolphin research and extension programs 7. Review of International Dolphin Conservation Program 8. Recommendations and Resolutions for 1997 9. Recommended research program and budget for FY 1998-1999

10. Place and date of next meeting 11. Election of officers 12. Other business 13. Adjournment The IATTC staff recommended a catch quota for yellowfin tuna and that steps be taken to

address the issue of the recent increases in the catches of small bigeye tuna. The following actions were taken: (1) A resolution regarding a catch quota for yellowfin was approved. This resolution reads as

follows: The Inter-American Tropical Tuna Commission, having responsibility for the scientific

study of the tunas and tuna-like fishes of the eastern Pacific Ocean, and for the formulation of recommendations to the High Contracting Parties with regard to these resources, and having maintained since 1950 a continuing scientific program directed toward the study of those resources,

Notes that the yellowfin tuna resource of the eastern Pacific supports one of the most important surface fisheries for tunas in the world, and

Recognizes, based on past experience in the fishery, that the potential production from the resource can be reduced by excessive fishing effort, and

9 ANNUAL REPORT 1997

Recalls that from 1966 through 1979 the implementation of asuccessful conservation program maintained the yellowfin stock at high levels of abundance, and

Notes that from 1980 through 1996, excepting 1987, although no conservation programs were implemented, conservation measures were recommended to the Commissioners by the scientific staff, and in turn such measures were approved by the Commissioners for recommendation to their respective governments, and

Observes that, although the stock of yellowfin is currently at a level of abundance greater than the optimum, nevertheless it can be over-exploited,

Concludes that, if conditions warrant, a limitation on the catch of yellowfin tuna should be implemented during 1997.

The Inter-American Tropical Tuna Commission therefore recommends to the High Contracting Parties that a quota of 220,000 metric tons be established for the 1997 calendar year on the total catch of yellowfin tuna from the CYRA (as defined in the resolution adopted by the Commission on May 17, 1962), and that the Director should be authorized to increase this limit by no more than three successive increments of 15,000 metric tons each if he concludes from examination of available data that such increases will pose no substantial danger to the stocks, and

Finally recommends that all member states and other interested states work diligently to achieve the implementation of such a yellowfin conservation program for 1997.

(2) Aresolution regarding bigeye tuna was approved. This resolution reads as follows: The Inter-American Tropical Tuna Commission (fATTC), having responsibility for the

scientific study of the tunas and tuna-like fishes of the eastern Pacific Ocean, and for recommending proposals, based on scientific evidence, for joint action by the High Contracting Parties designed to keep the populations of fishes covered by the Convention at levels of abundance that will permit the maximum sustained catches,

1. Notes that the annual catches of small bigeye tuna taken in the purse-seine fishery of the eastern Pacific Ocean have increased during the past few years from less than 5,000 metric tons to more than 50,000 metric tons;

2. Recognizes that such increases are likely to cause a reduction in the overall catches of bigeye tuna from the eastern Pacific;

3. Notes that a limitation of mortality generated by purse-seining for bigeye associated with noating objects to 1996 levels would prevent exacerbation of the problem;

4. Expresses concern that the fishery for bigeye associated with floating objects results in elevated catches of unmarketable bigeye as well as many other associated species being discarded to the sea dead;

5. Recalling that Article 5 of the United Nations Agreement for the implementation of the provisions of the United Nations Convention on the Law of the Sea of 10 December 1982 relating to the Conservation and Management of Straddling Fish Stocks and Highly Migratory Fish Stocks requires coastal states and fishing states to, inter alia, (1) adopt measures to ensure long-term sustainability of straddling fish stocks and highly migratory fish stocks and promote the objective of their optimum utilization, (2) ensure that such measures are based on the best scientific evidence available and are designed to maintain or restore stocks at levels capable of producing maximum sustainable yield, (3) apply the precautionary approach in accordance with Article 6 of the Agreement, (4) minimize pollution, waste, discards, catch by lost or abandoned gear, catch of non-target species of both fish and non-fish species, (5) protect biodiversity in the marine environment and (6) take measures to prevent or eliminate overfishing

10 TUNA COMMISSION

and excess fishing capacity; 6. Noting that the FAO Code of Conduct for Responsible Fisheries calls on states, inter

national organizations, and all those involved in fisheries to collaborate in fulfilling the objectives and principles of the Code, which include taking measures to prevent or eliminate excess fishing capacity and ensuring that levels of fishing effort are commensurate with the sustainable use of fishery resources; in the case of new or exploratory fisheries, adoption as soon as possible of cautious conservation and management measures, including, inter alia, catch limits and effort limits which should remain in force until there are sufficient data to allow assessment of the impact of the fisheries on the long-term sustainability of the stocks; and take appropriate measures to minimize waste, discards, and catch of non-target species, both fish and non-fish species;

7. Recalling further that the Declaration of Panama, concluded and adopted in October 1995 by twelve governments, and supported by five environmental groups, to formalize the La Jolla Agreement as a binding legal instrument which requires, inter alia, a commitment to adopt conservation and management measures that ensure the longterm sustainability of tuna stocks, and that such measures shall be designed to maintain or restore the biomass of harvested stocks at or above levels capable of producing maximum sustainable yields; and

8, Noting that the Declaration of Panama also calls on governments to take measures to avoid, reduce and minimize the bycatch of juvenile tuna and bycatch of non-target species, therefore:

9. Concludes that action should be taken to limit or reduce the fishing mortality of small bigeye tuna in the eastern Pacific Ocean to the levels observed in the fishery in recent years, the exact levels of such limitations and/or reductions to be considered at the 1998 Annual Meeting of the IATTC; and

10. Requests the staff of the IATTC to convene aWorking Group of experts to evaluate possible management options which can be implemented to achieve the objectives detailed in Paragraph 9, including consideration of, inter alia, closed areas, closed seasons, prohibitions and/or limitations on the use of certain types of fishing gear, global catch quotas, and individual vessel quotas; and

11. Finally recommends that the Working Group shall meet as frequently as necessary to achieve its objectives, but shall report to the High Contracting Parties its recommendations for conservation and management measures to achieve the objectives defined in Paragraph 5 above no later than the next Annual Meeting of the IATTC. (3) The proposed budget of $4,553,226 for the 1998-1999 fiscal year, was approved as presented.

It was suggested that simultaneous interpretation should be provided at future meetings of the IRP, and the staff agreed to look into the possibility of including this in future budgets.

(4) It was decided that a working group would be established to examine the question of bycatches of all species in the purse-seine fishery for tunas in the EPa, and look for ways of reducing it. The staff was instructed to prepare a document outlining the group's tenns of reference and some proposals for consideration, and distribute it among the governments. The staff would also select the members of the working group.

(5) It was agreed that the next regular meeting of the IATTC would be held in La Jolla, California, USA in June 1998.

Copies of the minutes of the meeting are available from the IATTe on request. The IATTC meeting was temporarily adjourned on June 4, and the 33rd IGM was convened. The


delegate from Mexico read a statement (Appendix 3) in which he declared his nation's intention of cautiously moving back toward full participation in the International Dolphin Conservation Program, which had been suspended in October 1996 (IATTC Annual Report for 1996, Appendix 2). The PresideI' at the 15th meeting of the IRP presented a report on the Panel's activities. The report included a recommendation that the Panel's Rules of Procedure be changed to allow any member nation of the IATTC, regardless of whether any purse-seine vessels with carrying capacities greater than 400 short tons were registered in that nation, to become a member of the Panel. Arevised version of the Rules of Procedure, incorporating changes adopted at the 32nd and 33rd IGMs, appears as Appendix 4of this report.

The minutes of the 33rd IGM are available from the IATTC on request.

59TH MEETING OF THE IATTe

The 59th meeting of the IATTC was held in La Jolla, California, USA, on October 28-31,1997. The purpose of the meeting was to negotiate a legally-binding agreement which would conform with the Declaration of Panama, passed at the 56th meeting of the lATTC, held in Panama, Republic of Panama, in October 1995 (IATTC Annual Report for 1995, Appendix 3). The agenda was as follows:

1. Opening of the meeting 2. Adoption of the agenda 3. Review of the 1997 fishing year to data 4. Review of the International Dolphin Conservation Program (IDCP) to date 5. Consideration for a legally binding instrument for the mcp 6. Other business 7. Adjournment

Because some of the nations which were to be involved in the negotiations are not members of the IATTC, the negotiations took place at the 34th IGM, described below.

Copies of the minutes of the meeting are available from the IATTC on request. The agenda for the 34th IGM was as follows: 1. Opening of the meeting 2. Election of Chairman 3. Adoption of agenda 4. Consideration of a legally binding instrument for the IDCP 5. Other business 6. Adjournment

Although considerable progress was made, agreement on a legally-binding instrument was not reached. It was agreed that another IGM would be held in January 1998 to continue the negotiations.

Copies of the minutes of the 34th IGM are available from the IATTC on request.

14TH MEETING OF THE IRP

The 14th meeting of the IRP was held in Santa Marta, Colombia, on February 18-19, 1997. Dr. Osvaldo Perez Molina of Colombia presided at the meeting, which was attended by representatives of Colombia, Costa Rica, the United States, Vanuatu, Venezuela, and the Camara Nacional de la Industria Pesquera of Mexico, plus representatives of the IATTC, acting as Secretariat.

The agenda consisted of the following items: 1. Opening of meeting 2. Election of PresideI' 3. Approval of agenda

12 TUNA COMMISSION

4. Approval of minutes of the 13th Meeting of the IRP 5. Dolphin Mortality Limits (DMLs):

a. Review of 1996 DMLs b. DMLs for 1997

6. Review of observer data 7. Gear requirements for vessels without DMLs 8. Possible inclusion in mcp of vessels of less that 400 short tons capacity 9. Observer identification cards

10. Procedures for dealing with special problem sets 11. Updating information on mortality rates in sets with few dolphins captured and no backdown 12. Membership of non-governmental organizations in the IRP 13. Confidentiality:

a. Names of vessels with DMLs b. Data release to coastal nations

14. Cooperation of nations not party to the Agreement with vessels in the EPO 15. DMLs and flag changes 16. Place and date of next meeting 17. Other business 18. Adjournment The IRP meeting was followed, on February 20-21, 1997, by the 32nd IGM, involving all the

national representatives at the IRP meeting, as either participants or observers, and also a representative from the Organizaci6n Latinoamericana de Desarrollo Pesquero. It was agreed to amend the wording in Part III of the Appendix to the Agreement for the Conservation of Dolphins related to the IRP so as to increase the number of representatives from non-governmental organizations (NGOs) on the Panel from four to six, three from environmental organizations and three from the tuna-fishing industry, all to be appointed by the member governments of the IRP. The revised version appears as Appendix 2of this report. It was also agreed that the government of Costa Rica would continue as a member of the Panel until the amendments to the Panel's composition are considered at the next meeting. Finally, it was agreed to accept the modified procedure for the entry of NGOs to the IRP proposed by an ad hoc committee of the IRP. The governments representatives at this meeting agreed on the Consensus of Santa Marta and the Resolution of Santa Marta, which appear as Appendices 5and 6 of this report.

Copies of the minutes of the 32nd IGM are available from the IATTC on request.


The 15th meeting of the IRP was held in Puntarenas, Costa Rica, on June 1-3, 1997. Sr. Jaime Basadre Oreamuno of Costa Rica presided at the meeting, which was attended by representatives of Colombia, Costa Rica, Ecuador, Mexico, Panama, the United States, Venezuela, the tuna industry, and the environmental community, plus representatives of the IATTC, acting as Secretariat.

The agenda consisted of the following items: 1. Opening of meeting 2. Election of Presider 3. Approval of agenda 4. Approval of minutes of the 14th Meeting of the IRP and 1996 IRP Annual Report 5. Observer identification cards 6. Gear requirements for vessels without DMLs 7. Time elapsed from start of set to end of backdown


8. Dolphin Mortality Limits (DMLs): a. Review of 1997 DMLs b. DMLs for the second semester of 1997

9. Review of observer data 10. Procedures for dealing with special problem sets 11. Confidentiality of information 12. Cooperation of nations not party to the Agreement with vessels in the EPa 13. Possible inclusion in mcp of vessels of less than 400 short tons capacity 14. Procedures for incorporation of government members to the Panel 15. Appointment of non-governmental members 16. Working group for the study of rules and procedures for entry of new fleets to the EPa 17. Place and date of next meeting 18. Other business 19. Adjournment


The 16th meeting of the IRP was held in La Jolla, California, on October 27,1997. Ms. Wanda Cain of the United States presided at the meeting, which was attended by representatives of Colombia, Costa Rica, Ecuador, Mexico, Panama, the United States, Vanuatu, Venezuela, the tuna industry, and the environmental community, plus representatives of the IATTC, acting as Secretariat.

The agenda consisted of the following items: 1. Opening of the meeting 2. Election of PresideI' 3. Approval of agenda 4. Approval of minutes of the 15th Meeting of the IRP 5. Dolphin Mortality Limits (DMLs):

a. Review of 1997 DMLs b. DMLs for 1998

6. Review of observer data 7. Procedures for dealing with special problem sets 8. Confidentiality of information

a. Vessels and DMLs b. IRP tuna vessel sighting form

9. Confirmation of vessel flag prior to participation in the mcp 10. Place and date of next meeting 11. Other business 12. Adjournment The latest version of the IRP Rules of Procedure, updated in accordance with decisions made at

the 32nd and 33rd IGMs, is shown in Appendix 4.

BIGEYE MANAGEMENT OPTIONS WORKING GROUP

Aresolution passed at the 58th meeting of the IATTC concluded "that action should be taken to limit or reduce the fishing mortality of small bigeye tuna in the eastern Pacific Ocean to the levels observed in the fishery in recent years," and requested that "the staff of the IATTC ... convene a Working Group of experts to evaluate possible management options which can be implemented to achieve" those

14 TUNA COMMISSION

"objectives," ... "including consideration of, intlJr alia, closed areas, closed seasons, prohibitions and/or limitations on the use of certain types of fishing gear, global catch quotas, and individual vessel quotas." The first meeting of the Bigeye Management Options Working Group was held in La Jolla, California, USA, OIl September 16-18,1997. The participants included experts on fisheries management from Canada, Colombia, Ecuador, Japan, Mexico, the United States, Venezuela, the South Pacific Commission, and the IATTC. The following agenda was adopted:

1. Welcome, introductions, housekeeping, and consideration of agenda 2. Introduction 3. Discussion of work schedule 4. Data collection and monitoring 5. Review of background papers 6. National means of compliance with any agreed measures 7. Discussion of suitable management options 8. Future work and timetable

Copies of the minutes of the meeting are available from the IATTC on request.

ADMINISTRATION

BUDGET

At its 55th meeting. held in La Jolla, Califol1lia, USA, on June 13-15, 1995, the Commission unanimously approved the budget for the 1996-1997 fiscal year, submitted by the Director, in the amount of $4,998,530. However, the final amount received from the member nations during the 1996-1997 fiscal year was $3,477,142"a shortfall of $1,521,358 relative to the amount which was recommended and approved for the regular budget. As a consequence, some planned research had to be curtailed. In addition to its regular budget, during the 1996-1997 fiscal year the IATTG received $1,234,573 from vessel owners to pay the costs of placing observers on their vessels, $34,407 from organizations which awarded contracts to the IATTC to perform various types of research, and $52,822 [rom interest and other sources.

FINANCIAL STATEMENT

The Commission's financial accounts for the 1996-1997 fiscal year were audited by Peat, Marwick, Mitchell and Co. Summary tables of its report are shown in Appendix 7 of this report.

INTER·AGENCY COOPERATION

During 1997 the scientific staff of the IATTC continued to maintain close contact with university, govel1lmental, and ptivate research organizations and institutions at local, national, and intel1lationallevels. This contact enabled the staff to keep abreast of the rapid advances and developments taking place in fisheries and oceanography research throughout the world. Some aspects of these relationships are described below.

The JATTC's headquarters are located on the campus of Scripps Institution of Oceanography (SIO), University of Califol1lia, La Jolla, California, USA, one of the major world centers for the study of marine science and the headquarters for federal and state agencies involved in fisheries, oceanography, and related sciences. This situation provides the staff with an excellent opportunity to maintain frequent contact with scientists of those organizations. Drs. James Joseph and Richard B. Deriso are mem


bers of the faculty of SIO, and Dr. Deriso supervised the research of some students at that institution during 1997. Ms. Cleridy E. Lennert-Cody and Mr. George M. Watters were registered as graduate students at SIO during 1997.

Drs. Joseph and Deriso also serve as members of the faculty of the University of Washington, Seattle, Wm;hington, USA, and Dr. Joseph is also a member of the faculty of the Universidad Aut6noma de Baja California, Ensenada, Mexico. Dr. Martin A. Hall serves as a member of the faculty of the University of British Columbia, Vancouver, B.C., Canada. Drs. Deriso, Hall, Michael G. Hinton, Robert J Olson, and Michael D. Scott served on committees which supervised the research of graduate students at various universities during 1997.

The cordial and productive relationships which the IATTC has enjoyed with the Comision Permanente del Pacifico Sur (CPPS), the Commission for the Conservation of Southern Bluefin Tuna (CCSBT), the Pood and Agriculture Organization (FAO) of the United Nations, the Indian Ocean 'l\ma Commission (lOTC) (fonnerly the Indo-Pacific Tuna Development and Management Programme (lPTP)), the lnternational Commission for the Conservation of Atlantic '!\mas (ICCAT), the Organizacion Latinoamericana de Desarrollo Pesquero (OLDEPESCA), the South Pacific Commission (now the Secretariat of the Pacific Community; SPC), and other international organizations have continued for many years. Mr. Alejandro A. Anganuzzi was granted two leaves of absence during 1997, one to work for the IPTP in Colombo, Sri Lanka, and the other to work as a consultant for FAO on a bioeconomic model for demersal fisheries for the government of Sri Lanka. To help achieve the objectives of its Expe11 Consultation on Interactions of Pacific Ocean Tuna Fisheries, FAO has prOvided funding for two computer simulation studies which are being conducted by the IATTC staff. FAO also provided funds for publication of the proceedings of a world workshop on bigeye tuna which was held at the IATTC headquarters in La Jolla in November 1996. Dr. Deriso served as an advisor for the CCSBT, and also as a member of a committee to review the adult sea lamprey program of the Great Lakes Fishery Commission, during 1997.

Also dming 1997 the IATTC staff maintained close working relationships with fishery agencies of its member countries, and with similar institutions in many non-member countries in various parts of the world. Mr. FOlTest R. Miller's studies of the effects of environmental conditions on the surface fishery for tunas, described in the subsection entitled Oceanography and meteorology, are funded by Continental Weather Services, Inc., and the U.S. National Oceanographic and Atmospheric Administration. Dr. James Joseph was a member of the Committee on Fisheries of the Ocean Studies Board of the U.S. National Academy of Sciences, Dr. Richard B. Deriso was co-chainnan of the Committee on Fish Stock Assessment Methods of the National Research Council of the United States, a member of the Scientific and Statistical Committee of tbe Western Pacific Fishery Management Council of the United States, a member of the Review Committee for California Sea Grant, and an advisor on stock assessment of school sharks to the Australian Fisheries and Management AuthOlity. Dr. William H. Bayliff and Mr. Patrick K. Tomlinson were members of the editorial board of Investigaciones Marinas GIGIMAR, published by the Centro Interdisciplinario de Ciencias Marinas, Instituto Politecnico Nacional, La Paz, Mexico, Dr. Ashley J. Mullen was Associate Editor of Natural Resource Modeling, a journal published by the Rocky Mountain Mathematics Consortium in association with the Resource Modeling Association, and Dr. Michael D. Scott was an Associate Editor of the journal Marine Mammal Science. Dr. Scott was also a member of the Pacific Scientific Review Group, which has the responsibility of monitoring U.S. marine mammal management policies and research in the Pacific Ocean. Mr. Kurt M. Schaefer participated in the Hawaii 'l\ma Tagging Program, funded by the Pelagic Fisheries Research Program at the Joint Institute of Marine and Atmospheric Research, School of Ocean and Earth Sciences and Technology, University of Hawaii at Manoa (see subsection entitled 'lUna tagging). Mr. Felipe Galvan-Magaiia of CICIMAR and Dr. Robert J. Olson of the IAITe continued their joint study of the

16 TUNA COMMISSION

trophic interactions of yellowfin tuna, dolphins, and associated predators in the eastem Pacific Ocean described on pages 27-28 of the IATTC Annual Report for 1995. Dr. Olson and Ms. Jenny M. Suter spent the period of June 2-July 7, 1997, in Japan. Their trip was supported by the Overseas Fishery Cooperation Foundation (OFCF) of Japan. While in Japan they visited two laboratories of the Japan Sea Farming Association, the Yaeyama Station on Ishigaki Island, Okinawa Prefecture, and the Amami Station on Amami Island, Kagoshima Prefecture, where they observed mariculture techniques. Dr. Olson also spent 2 weeks at the Fisheries Research Station of Nagasaki University in Nomozaki, where he worked with several facuIty members on respirometry techniques. Ms. Suter also spent 2weeks at the Ocean Research Institute of Tokyo University, where she worked with the staff on identification and ecology of zooplankton commonly found in the stomachs of tuna larvae. Dr. Daniel Margulies and Ms. Jeanne Wexler of the IATTC and Dr. Seinen Chow of the National Research Institute of Far Seas Fisheries of Japan collaborated on analyses of the genetics and age and growth of yellowfin and/or bigeye tuna collected offshore off Panama. Also, Dr. Chow, Dr. Berten E. Ely of the University of South Carolina, USA, and Dr. Peter Grewe of the Commonwealth Scientific and Industrial Research Organization, Australia, continned species identifications from tissue samples of specimens of yellowfin and bigeye tunas utilized in a comparative study of some anatomical features of these two species conducted by Mr. Kurt M. Schaefer of the IATTe. This work is described in the subsection entitled Identification of yellowfin and bigeye tUlia. At the invitation of Dr. Christofer H. Boggs of the U.S. National Maline Fisheries Service (NMFS), Honolulu, Hawaii, Dr. Michael G. Hinton participated on a swordfish research cruise aboard the NMFS vessel Townsend Oromwell in the EPG, mostly between 5°N and looN in the vicinity of 140oW, from August 30 to September 29, 1997. This work is described in the subsection entitled Swordfish studies. Ms. Wexler participated in a course entitled Identification of the Early Stages of Fishes in the Soulhem Region of the California Current, given at the Centro Interdisciplinario de Ciencias Marinas of the Instituto Politecnico Nacional, in La Paz, Mexico, on December 8-12, 1997. The course was taught by members of the staff of the U.S. NMFS, La Jolla, California.

Since 1977 the IATTC staff has been training observers for placement aboard tuna vessels to collect data on abundance, mortality, and other aspects of the biology of dolphins. In addition, these observers have collected stomach contents and samples of gonads and other tissues of tunas, recorded data on the incidental catches of species other than tunas and dolphins, recorded infonnation on floating objects and the fauna and flora associated with them, etc. Govermnent organizations, educational institutions, and industry representatives from the various countries involved have cooperated fully in the training and placement of these observers. Data collected by the observer program of Mexico were furnished to the IATTC staff for analysis.

Over the years, scientists and students from many countries have spent several weeks or months at the IATTe's headquarters in La Jolla and at its Achotines Laboratory learning new research methods and conducting research utilizing L


ects on species other than tunas, e.g. corvina-like flshes (Sciaenidae) and snappers (Lutjanidae), discussed in the subsection entitled Spawning and rearing ofpolla drum and spotted rose snappers.

Late in 1993, an agreement was reached by the OFCF of Japan, the government of the Republic of Panama, and the IATTC to undertake a joint five-year project, funded mostly by the OFCF, at the Achotines Laboratory. The project, which entered its initial stage in 1994, encompasses research on the feasibility of culturing adult yellowfin tuna, corvina-like fishes, and snappers to supply larvae for research, and the production of food organisms for their larvae and juveniles. This project is described in the section entitled Early life history studies. In October 1997 it was recommended that the project be extended by an additional two years.

Over the years, IATTC employees have collected tissue samples of tunas and billfishes for use in genetic studies conducted by scientists of other organizations. In 1997 samples of tissues of vm10us species of tuna and tuna-like fishes were collected for the Division of Fisheries, Commonwealth Scientific and Industrial Organization, Hobart, Australia, the National Research Institute of Far Seas Fisheries (NRIFSF), Shimizu, Japan, the FISHTEC Genetics Laboratory, University of South Carolina, Columbia, South Carolina, USA, the Rowett Research Institute, Aberdeen, Scotland, and the Virginia Institute of Marine Sciences (VIMS), College of William and Mary, Gloucester Point, Virginia, USA. (The IATTC also contributes financial support to some of the studies conducted at the VIMS.)

FIELD STATIONS

The IATTC maintains field offices in Manta, Ecuador; Ensenada and Mazathin, Mexico; Panmua, Republic of Pananm; Mayaguez, Puerto Rico, USA; and Cunlana, Venezuela. The scientists and technicians stationed at these offices collect landings data, abstract the logbooks of tuna vessels to obtain catch and effort data, measure flsh and collect oilier biological data, and assist with the training and placement of observers aboard vessels participating in the IATTC's Tuna-Dolphin Program. This work is carried out not only in the above-nmned ports, but also in other ports in Colombia, Costa Rica, Ecuador, Mexico, Panama, Pern, Puerto Rico, and Venezuela, which are visited regularly by IATTC employees.

In addition, the IATTC maintains a laboratory at Achotines Bay, just west of Punta Mala on the Azuero Peninsula of Panama. The Achotines Laboratory is used principally for studies of the early life history of tunas. Such studies are of great importance, as acquisition of knowledge of the life history of tunas prior to recruitment into the fishery would reduce the uncertainty which currently exists in the staff's assessments of the condition of the various stocks of tunas. The enlargement of the laboratory facilities to accommodate the previously-described project involving the Overseas Fishery Cooperation Foundation of Japan, the government of Panmua, and the IATTC was completed during 1997. The work conducted at the Achotines Laboratory is described in the section entitled Early life history stUdies.

PUBLICATIONS

The prompt and complete publication of research results is one of the most important elements of the IATTC's program of scientific investigations. By this means the member governments, the scientific community, and the public at large are currently informed of the research findings of the IATTC staff. The publication of basic data, methods of analysis, and conclusions afford the opportunity for critical review by other scientists, ensuring the soundness of the conclusions reached by the IATTC staff and enlisting the interest of oilier scientists in the IATTC's research. By the end of 1997 IATTC staff members had published 141 Bulletins, 46 Annual Reports, 8 Special Reports, 9 Data Reports, 8 books, and 478 chapters, papers, and articles in books and outside journals. The contributions by staff members published during 1997 are listed in Appendix 8 of this report.

18 TUNA COMMISSION

TUNA-BILLFISH PROGRAM

THE FISHERY

The JATTC staff is concerned plincipally with the eastern Pacific Ocean (EPO; Figure 1), currently defined, for purposes of catch and effort statistics, as the area between the mainland of North, Central, and South America and 150°W.

The eastern Pacific tuna fleet

The JATTC staff maintains records of gear, flag, and fish-carrying capacity for most of the vessels which fish at the smface for yellowfin (Thunnus albacares), skipjack (Katsuwonus pelamis), bigeye (Thunnus obesus), or bluefin (T. thynnus) tuna in the EPO. Records are not maintained for Far Eastflag longline vessels, nor for sport-fishing vessels and small craft such as canoes and launches. The fleet desclibed here includes vessels which have fished all or part of the year in the EPO for yellowfin, skipjack, bigeye, or bluefin tuna.

The owner's or builder's estimates of vessel carrying capacities are used until landing records indicate that revision of these is appropriate. The vessels are grouped, by carrying capacity, into the following size classes for reporting purposes: class 1, less than 51 short tons (ST) (46 metric tons (MT)); class 2,51-100 ST (46-91 MT); class 3,101-200 ST (92-181 MT); class 4,201-300 ST (182·272 MT); class 5, 301-400 ST (273-363 MT); and class 6, more than 400 ST (363 MT). Except for longliners and the miscellaneous small vessels mentioned in the previous paragraph, all vessels which fished in the EPO during the year are included in the annual estimates of the size of the surface fleet.

Until about 1960 fishing for tunas in the EPO was dominated by baitboats operating in the more coastal regions and in the vicinity of offshore islands. During the late 1950s and early 1960s most of the larger baitboats were converted to purse seiners, and by 1961 the EPO surface fleet was dominated by these vessels. During the 1961-1991 period the number of baitboats decreased from about 93 to 19, where it has since remained, and their total capacity decreased from about 10 to 1thousand metric tons. During the same period the number of purse seiners increased from 125 to 155, and their capacity increased from about 27 to 108 thousand metric tons. The peak in numbers and capacity of purse seiners occurred from the mid-1970s to the early 1980s, when the maximum number of vessels, 282, and the maximum capacity, about 168 thousand metric tons, were reached (Table 1).

The construction of new and larger purse seiners, which began during the mid-1960s, resulted in an increase in the total surface fleet capacity from about 42 thousand metric tons in 1966 to about 167 thousand metric tons in 1976. During the 1977-1981 peliod the fleet capacity remained fairly stable. Duling this period the construction of new vessels continued, but the new capacity was offset by losses due to sinkings and vessels leaving the fishery. Amajor El Nino event began in mid-1982 and persisted until late 1983. The catch rates in the EPO were low during the 1978-1981 period due to concentration of fishing effort on small fish, and the situation was exacerbated by the EI Nino episode, which made the fish less vulnerable to capture. In 1982 the fleet capacity declined by about 16 thousand metric tons as vessels were deactivated or left the EPO to fish in other areas, primarily the western Pacific. This trend continued through 1983 as the catch rates in the EPO declined further, and the fleet capacity declined by about 48 thousand metric tons during 1983 and 1984. The fleet capacity in 1984, about 107 thousand metric tons, was the lowest it had been since 1971. In 1985, however, due plimarily to the return of vessels from the western Pacific, the capacity increased to about 120 thousand metric tons, but in 1986 it decreased slightly to about 114 thousand metric tons. During 1987, several new vessels were added to the fleet, and others returned to the EPO fishery from the western Pacific, causing the fleet capacity to increase to about 132 thousand metric tons. This trend continued in 1988, resulting in a fleet capacity of about 137 thousand metric tons. This was the greatest fleet capacity since 1982. In


the spring of 1990 the U.S. tuna-canning industry adopted a policy of not purchasing tunas caught during trips during which sets on tunas associated with dolphins were made. This caused many of the U.S.flag vessels fishing in the EPO to leave that fishery and enter the fisheries of the Atlantic or western Pacific. The U.S. canners have continued their "dolphin-safe" policy, resulting in further decreases in the number of U.S.-flag vessels fishing in the EPO, and a consequent reduction in the EPO fleet to about 101 thousand metric tons in 1992. With increases in participation of non-U.S.-flag vessels in the fishery, the capacity has increased steadily since 1992, and the 1997 capacity was about 129 thousand metric tons.

The 1996 and preliminary 1997 data for numbers and carrying capacities ofsurface-gearvessels ofthe EPO tuna fleet are shown in Tables 2a and 2b. The EPO tuna fleet was dominated byvessels operating under the Mexican and Ecuadorian flags during 1997. The Mexican fleet has been the largest fleet since 1987, with about 33 percent of the total capacity during 1997, while vessels registered in Ecuador, Venezuela, Vanuatu, and the United States complised 19, 17,9, and 8percent of the total capacity, respectively.

Class-6 purse seiners make up the majority of the total capacity of the fleet of vessels which fish at the surface for tunas in the EPO. This group of vessels comprised 89 percent of the total fishing capacity operating in the EPO in 1997.

The monthly average, minimum, and maximum capacities at sea (CAS), in metric tons, of vessels which fished at the surface for tunas in the EPO during 1982-1996, and the 1997 values, are shown in Figure 2. The monthly values are averages of the CAS estimates given in the Weekly Reports prepared by the JATTC staff. The values for the 1982-1996 period were chosen for comparison with those of 1997 because the earlier years, when regulations were in effect, had somewhat different temporal distlibutions of effort due to restriction of yellowfm fishing in the Commission's Yellowfin Regulatory Area (CYRA; Figure 1). Overall, the 1997 CAS values are greater than the 1982-1996 averages. During the 19821996 period an average of 51 percent of the fleet capacity was at sea during each month; in 1997 the average was about 59 percent. Thus, while the total capacity of the fleet in 1997 was lower than in many of the previous years, the ratio of the CAS to the total fleet capacity was greater than the average observed during the preceding 15-year peliod. The extremes in the average monthly CAS were observed in 19831984, during and following the 1982-1983 E1 Nino event, when the average monthly CAS was about 38 percent, and in 1989, when the average monthly CAS was about 61 percent.

Catches

Annual estimates of the catches of the various species of tunas and other fishes landed by vessels of the EPO fleet which fish for tunas with surface gear are shown in Table 3. The subsurface Gongline) catches of yellowfin, bigeye, and bluefin in the EPO are listed in Tables 14, 15, 16, and 27, and data for those species and black skipjack (Euthynnus lineatus) discarded at sea in the EPO are listed in Table 40. The data for skipjack which are landed are essentially complete except for insignificant catches made by the longline, sport, and artisanal fisheries. Recreational catches landed in California are included in the landings. In the case of bluefin, these landings have become an increasingly important component of the catch in recent years (Table 27).

There were no restlictions on fishing for tunas in the EPO during the 1982-1997 peliod, although regulations placed on purse-seine vessels directing their effort at tunas associated with dolphins have probably affected the way these vessels operate, especially during the late 1980s and the 1990s. Studies which may provide measures of this effect are currently in progress, but useful results are not yet available, so the statistics for 1997 are compared to those for 1982-1996. As mentioned in the previous subsection, there was a major EI Nifio event during 1982-1983 which made the fish less vulnerable to capture and reduced the numbers of vessels in the EPO. The fishing effort remained relatively low during 1984-1986.

The average annual catch of yellowfm by smface gear in the CYRA during the 1982-1996 peliod was 197 thousand metlic tons (range: 82 to 267 thousand). The preliminary estimate of the 1997 yellowfm

20 TUNA COMMISSION

catch in the CYRA is 219 thousand metric tons. During the 1982-1996 period the annual yellowfin catch by surface gear in the area between the CYRA boundary and 1500Waveraged 26 thousand metric tons (range: 12 to 47 thousand). The preliminary estimate of the yellowfin catch from this area for 1997 is 41 thousand metric tons. The estimated 1997 yellowfin catch from the EPO, 260 thousand metric tons, is below the maximum of 289 thousand metric tons taken in 1989, but about 14 percent greater than the 1982-1996 average of 223 thousand metric tons.

During the 1982-1996 period the annual catch of skipjack in the EPO averaged 83 thousand metric tons (range: 49 to 138 thousand). The preliminary estimate of the skipjack catch in the EPO in 1997, 158 thousand metric tons, is nearly 90 percent greater than the average of the annual catches for the last 15 years. The 1997 skipjack catch has exceeded those of all previous years except 1978, when 170 thousand metric tons were caught).

Prior to 1994 the average catch of bigeye in the EPO by surface gear was about 4 thousand metric tons (range:


exploring methods to combine the two data bases, retaining only the more reliable data in cases where there is duplication.) The greatest numbers of sets on schools associated with floating objects and on schools of tuna associated only with other fish were made during the period from the mid-1970s to the early 1980s. Despite opposition to fishing for tunas associated with dolphins and the refusal of U.S. canners to accept tunas caught during trips during which sets were made on dolphin-associated fish, the numbers of sets made on fish associated with dolphins have decreased only moderately. The logged catches of tunas in these sets peaked at about 173 thousand metric tons in 1989, and then decreased to about 106 thousand metric tons in 1993. Since then the logged catches taken in dolphin sets have increased, averaging about 128 thousand metric tons during 1994-1997.

The average annual distribution of the logged catches of yellowfrn by purse seiners in the EPO during the 1982-1996 period is shown in Figure 3, and a preliminary estimate for 1997 is shown in Figure 4. In 1997 the catches were relatively greater south of the equator and west of about 83°W. As fishing conditions change throughout the year, the areas of greatest catches vary. The catch of yellowfrn during the first quarter of 1997 was generally restricted to regions inside the CYRA, primarily in nearshore areas along the coast of North and Central America, in the vicinity of the Costa Rica Dome, and between about 5°N and lOON from about 85°W to 108°W. In addition, good fishing occurred offshore in the southern hemisphere between about 0° and 15°S from about 800Wto 97°W. During the second quarter substantial catches continued to be made nearshore, especially at entrance of the Gulf of California and near the Costa Rica Dome. The catches increased in the offshore area between about 5°N and 15°N from about 1l00W to 133°W, along the confluence of the North Pacific Current and the westward-flowing North Equatorial Current (NEC) and along the boundary between the NEC and the eastward-flowing Equatorial Countercurrent. During the third quarter, regions of relatively high catches OCCUITed (l) off Baja California between about 24°N and 300N, (2) near the Costa Rica Dome, and (3) in the offshore region between about 8°N and 22°N from about 112°W to 130°W. The catches declined during the third quarter in the nearshore region off Colombia and Ecuador. During the fourth quarter fishing continued throughout most of the EPO, with areas of high catches scattered over the region. Somewhat concentrated areas of higher catches were located between about 8°N and 200Nfrom about 92°W to 125°W and near the Galapagos Islands. Also, the catches increased in the Gulf of California, but decreased in the area off Baja California. Relatively small amounts of yellowfin were caught south of the equator during the second, third, and fourth quarters.

The average annual distribution of the logged catches of skipjack by purse seiners in the EPO during the 1982-1996 period is shown in Figure 5, and a preliminary estimate for 1997 is shown in Figure 6. In 1997 the catches were relatively greater south of the equator and west of about 100°W. High catches of skipjack were made during the fIrst quarter of 1997 between about 50Sand 17°S from about 800W to 90°W. Another extensive region of high catches was located well offshore between about 2°S and 11 oS from about 108°W to 135°W. Less extensive areas of high catches were also located in the Panama Bight and in the region between about WON and 2°S from about 89°W to 107°W. During the second quarter the zone of relatively high catches in the Panama Bight extended southward off the coasts of Colombia and Ecuador and westward to about 90°W. The extensive zone of high catches in the offshore region extended from about 82°W to 138°W between about 3°S and 14°S. Also during the second quarter the catches of skipjack increased significantly in the area between about 5°N and 15°N from about 95°W to 137°W and near the entrance of the Gulf of California. During the third quarter the catches declined in the offshore zone south of about 2°8 and in the Gulf of Panama and off northern Colombia. The catches remained high off southern Colombia and off Ecuador to about 95°W. The catches increased in the area between about 8°N and 22°N from about 115°W to 130°W. The catches declined in the Gulf of California, but increased significantly off Baja California from about 24°N to 32°N. As the year progressed, the catches continued to decrease in the Panama Bight, and by the fourth quarter there remained only a few scattered regions of higher catches off the coast of Ecuador. During the fourth quarter regions of high catches were widely distlibuted in the offshore regions of the EPO and along the

22 TUNA COMMISSION

Inter-Tropical Convergence Zone from the coast of Ecuador to about 125°W. Also during the fourth quarter the catches increased in the Gulf of California, but declined off Baja California. The catches also declined in the offshore area between about 8°:'-/ and 200Nfrom about 105°W to 125°W.

The average annual distribution of the logged catches of bigeye by purse seiners in the EPO during the 1994-1996 period is shown in Figure 7, and a preliminary estimate for 1997 is shown in Figure 8. The catch of bigeye by surface gear during the 1994-1996 period was made in two principal areas, (1) between about 6°N and 100S from about 900Wto 130oW, and (2) between about 3°N and 3°S from about 82°W to 88°W (Figure 7). With the development of the fishery for subsurface tunas associated with floating objects, described above, the relative importance of the nearshore areas has decreased, while that of the offshore areas has increased. In 1997, as during the 1994-1996 period, relatively large bigeye catches were made between about 6°N and 100S from about 900Wto 1300Wduring all quarters (Figure 8). Bigeye were taken in the nearshore area between 3°N and 3°S from about 82°W to 88°W, primarily during the second, third, and fourth quarters.

Under the tenus of the convention which established the IATTC, the Pl1mary objective of the IATTC staff's research is monitoring the condition of the stocks of tunas and other species taken in the EPO by tuna fisheries. Taking into consideration the extensive movements of the tunas, the mobility of the vessels of the tuna fleets of various nations, and the international nature of the tuna trade, statistics on the catch and effort from the EPO must be viewed in the light of global statistics. Statistics for the global catches of tunas and related species for 1996, the most recent year for which data are available, are presented in Figures 9and 10. Statistics of the catches of the principal market species of tunas during 1970-1996, by oceans, appear in Table 6 and Figure 11.

Catch per ton of carrying capacity

The total catch per ton of can)'ing capacity (CPTCC) for the vessels which fish at the surface for tunas in the EPO provides an index of trends in annual relative gross income for vessels of various size groups. To provide more detail in this index than would be available if the IATTC's historical six classes of vessel capacity classification were used, the vessels are assigned to following size groups: 1, 1400 ST (1270 MT).

Estimates of the CPTCCs for the 1986-1997 period are presented in Table 7for the EPO and for all ocean fishing areas from which vessels of the EPO tuna fleet harvested fish, by size group, area, and species. Yellowfin and skipjack contribute the most to the CPTCCs for the larger vessels, while other species, which include other tunas as well as miscellaneous fishes, make up an important part of the CPTCCs of the smaller vessels in many years. In earlier years, and in years in which the majority of the EPO tuna fleet exerts most of its fishing effort in the EPO, the CPTCCs for the EPO and all ocean fishing areas are nearly the same. During the 1986-1996 period the CPTCCs in the EPO for all vessels and all species averaged 3.2 tons of fish per ton of carrying capacity, with a range of 2.6 to 3.8; for yellowfin it averaged 2.2 tons, with a range of 2.1 to 2.4; and for skipjack it averaged 0.8 tons, with a range of 0.5 to 1.2. The preliminary estimates for 1997 are 3.8, 2.1, and 1.3 tons for all species, yellowfin, and skipjack, respectively. The only years in which yellowfin and skipjack combined constituted less than 90 percent of the total are 1994-1997.

YELLOWFIN QUOTAS

The scientific staff of the IATTC has the responsibility for conducting studies of the biology of the tunas and related species of fish inhabiting the eastern Pacific Ocean and the effects of fishing upon


them, and recommending appropriate conservation measures when necessary so that the stocks of fish can be maintained at levels which will yield the maximum sustainable catches. The Director first recommended that an annual quota be set on the catch of yellowfin in the Commission's Yellowfin Regulatory Area (CYRA; Figure 1) in 1962. However, the member govemments could not reach agreement on a yellowfin quota until 1966. Agreement was reached on a quota for every year from 1966 through 1986 and 1988 through 1997. The Director did not recommend a quota for 1987 because, due primarily to exceptionally high levels of recruitment in 1984 and 1985, the abundance of yellowfin appeared to be at its greatest level in recent years.

The IATTC held its 58th meeting in San Jose, Costa Rica, on JWle 3-4, 1997. The Director recommended a yellowfin quota of 220,000 metric tons for that year, with the option to increase this limit by up to three increments of 15,000 metric tons each. This quota was also adopted.

RESEARCH

Size composition of the catch

Length-frequency samples are the basic source of data used for estimating the size and age compositions of the various species of fish in the landings. This information is necessary to obtain age-structured estimates of the population for various purposes, including age-structured population modeling. The results of age-structured population modeling can be used to estimate recruitment, which can be compared to spawning biomass and oceanographic conditions. Also, the estimates of mortality obtained from age-stmctured population modeling can be used, in conjunction with growth estimates, for yieldper-recruit modeling. The results of such studies have been described in several IATTC Bulletins and in all of its Annual Reports since that for 1954.

Length-frequency samples of yellowfin, skipjack, bigeye, northem bluefin, and black skipjack from purse-seine, baitboat, and recreational catches made in the eastern Pacific Ocean (EPO) are collected by IATTC personnel at ports of landing in Ecuador, Mexico, Panama, the USA (California and Puerto Rico), and Venezuela. The catches of yellowfin and skipjack were first sampled in 1954, and sampling has continued to the present.

The staff collected and processed 742 yellowfin, 554 skipjack, 192 bigeye, 26 northern bluefin, and 17 black skipjack samples from the 1997 catch. Most of these were 50-fish samples. For all of the above species except black skipjack the length-frequency samples are stratified by market-measurement areas (Figure 12), months, and years. The sampling procedures are explained in detail in IATTC Bulletin, Vol. 20, No.6.

Figure 13 consists of histograms showing the estimated catches of yellowfin in the market-measurement areas of the EPa (Figure 12) in 1997. Although the size range is approximately the same in all areas, with nearly all of the fish being between 40 and 160 cm in length, the distributions differ considerably from area to area. The average weights range from 3.0 kg (6.7 pounds) in Area 6 to 14.1 kg (31.1 pounds) in Area 10.

Histograms showing the estimated catches of yellowfin in the CYRA (all areas except 10 and 11 in Figure 12) during each year of the 1992-1997 period appear in Figure 14. The average weight for 1997, 9.1 kg (20.0 pounds), was the lowest for the 1992-1997 period.

Figure 15 consists of histograms showing the estimated catches of yellowfm in the area between the CYRA boundary and 1500 W(Areas 10 and 11 in Figure 12) during each year of the 1992-1997 period. The largest modal group in the 1997 distribution is located between 90 and 140 cm. The distribution is somewhat similar to those of 1995 and 1996, but the relative frequency of fish between about 90 and 120 cm was greater during 1997 than during the other two years. The average weight for 1997, 13.8 kg (30.4 pOlwds), was the lowest for the 1992-1997 period.

24 TUNA COMMISSION

Histograms showing the estimated catches of skipjack in the market-measurement areas of the EPO in 1997 appear in Figure 16. The data for Areas 1, 2, and 8 and Areas 4 and 5 have been combined due to low catches in those areas (Figure 6). Larger fish are most evident in Area 7, and smaller fish are most evident in Areas 7, 13, and 11.

Figure 17 consists of histograms showing the estimated catches of skipjack in the entire EPO for each year of the 1992-1997 period. The average weight for 1997, 2.4 kg (5.3 pounds), was the lowest of the 6-year period.

Prior to 1994 the surface catch of bigeye in the EPO was incidental to that of yellowfin and skipjack, and the annual catches (Table 3) and numbers of length-frequency samples taken were considerably less than those of yellowfin and skipjack. During 1994-1997, however, more bigeye were caught and more samples were obtained. Histograms showing the estimated catches of bigeye in the marketmeasurement areas of the EPO during 1997 appear in Figure 18. The greatest catches occurred in Areas 7and 11. The larger fish evident in Areas 7 and 9 are viltually absent in the other areas.

Figure 19 consists of histograms showing the estimated catches of bigeye during each year of the 1992-1997 period. The average weight for 1997, 5.4 kg (12.0 pounds), was the lowest of the 6-year period.

Northern bluefm are caught by surface gear off California and Baja California from about 23°N to 35°N, with most of the catch being taken during May through October. During 1997 bluefin were caught between 27°N and 33°N, and most of the catch was taken during July and August. Histograms showing the estimated catches of bluefin during each year of the 1992-1997 period appear in Figure 20. The numbers of samples obtained from commercial and recreational catches during recent years were as follows:

Year Commercial Recreational

1990 14 o 1991 4 o 1992 1 1 1993 4 35 1994 2 11 1995 6 16 1996 67 5 1997 17 9

The incidence of larger fish was greater in the catches of the commercial vessels. Four distinct modal groups, corresponding to 2-, 3-, 4-, and 5-year-old fish, are evident in the data for 1996.

Black skipjack are caught incidentally by fishermen who are directing their effort toward yellowfin, skipjack, and bigeye tuna. The demand for this species is low, so most of the catch is discarded at sea, but small amOlmts, mixed with the more desirable species, are sometimes retained. Annual percentage length-frequency distributions of black skipjack caught in the EPO during 1992-1997 are shown in Figure 21. The average weight for 1994 was much less than those for the other years, but this may not be significant, as the sampling during that year was inadequate. No attempt has been made to estimate the weights of the catches by size intervals.

Identification of yellowjin and bigeye tuna

Acomparative study of the anatomical features of yellowfin and bigeye tuna is nearing completion. Statistical analyses of the external and internal anatomical characteristics for which data had been collected were completed during 1997. The objective of this research is to provide valid diagnostic features for the separation of these two species throughout the size range taken by the commercial fisheries of the eastern Pacific Ocean.


The 58 bigeye and 62 yellowfm utilized in this study were captured by purse-seine vessels fishing near fish-aggregating devices (FADs) in the area encompassed by 3"N, 7"S, 100oW, and 144°W during July 1996 through January 1997. They ranged in length from about 35 to 145 cm. The species were identified by the morphology of their livers. Samples of muscle tissue of all specimens were sent to three geneticists, Dr. Seinen Chow of the National Research Institute of Far Seas Fisheries, .lapan, Dr. Berten E. Ely of the University of South Carolina, USA, and Dr. Peter Grewe of the Commonwealth Scientific and Industrial Research Organization, Australia, all of whom confirmed the species identifications.

Each specimen was examined for coloration and distinctive markings, weighed, and sexed. Fifteen different body dimensions were measured, the gill rakers were counted, data on the liver and swim bladder size and morphology were recorded, the otoliths were removed, and a muscle sample was taken. Each of 14 morphometric relationships (ratios of 14 of the measurements to the fork length (length from the tip of the snout to the fork of the tail)) for each species was evaluated by fitting weighted nonlinear regressions to the untransfonued data sets. The regression relationships which were found to have statistically-significant differences and to be practical for distinguishing bigeye and yellowfin are: (I) head length versus fork length; (2) eye diameter versus fork length; (3) distance from origin of first dorsal fin to origin of pelvic fin versus fork length; (4) pectoral fin length versus fork length; (5) second dorsal fin length versus fork length; and (6) anal fin length versus fork length.

The total gill raker counts were significantly greater for yellowfin (mean = 30.38; range = 28-33) than for bigeye (mean = 26.55; range = 25-29). The morphology of the livers of yellowfin and bigeye are quite different. In yellowfin the right lobe of the liver is considerably longer than the medial and left lobes, whereas in bigeye the medial lobe is slightly longer than the right and left lobes. Striations are absent from the liver in yellowfin, but present along the ventral edges of the lobes in bigeye. Estimates of the swim bladder volumes for the two species were computed from geometric reconstructions of the bladders based on measurements of the dimensions. For fish of the same size, the volume is significantly greater for bigeye than for yellowfin.

Reproductive biology ofskipjack tuna

A2-year sampling progran1 of skipjack tuna gonads, carried out by observers aboard purse-seine vessels fishing in the eastern Pacific Ocean (EPO), was initiated in January 1996 and completed in December 1997. The objective is to obtain a comprehensive understanding of the reproductive biology and reproductive potential of skipjack in the EPa. This project is described in more detail in the IATTC Annual Report for 1996.

As of the end of 1997, samples had been taken on 64 trips, producing 3,710 females with ovarian tissues suitable for histological processing and examination. The tissue samples will be processed and slides will be prepared during 1998. These slides will be examined microscopically to identify the stages of oogenesis, providing an accurate assessment of the reproductive status of each fish. Ovaries are also being selected during the processing to be used for estimating the fecundity of the fish.

Effects ofclosure ofseason-area strata on the catches of bigeye and other species of tunas

At the 58th meeting of the IATTC a resolution was adopted requesting that "the staff of the IATTC ... convene a Working Group of experts to evaluate possible management options which can be implemented to" ... "limit or reduce the fishing mortality of small bigeye tuna in the eastern Pacific Ocean to the levels observed in the fishery in recent years." This section describes the results of a study of the effects of one option, closure of season-area strata, on the catches of bigeye and other species of tunas, which was presented as a background paper to the first meeting of that working group.

Data collected by observers for the IATTC Tuna-Dolphin Program during 1994, 1995, and 1996 were stratified by 5-degree areas and quarters. During those years at least 94 percent of the bigeye were caught

26 TUNA COMMISSION

in association with floating objects, so only data pertaining to this type of set were considered in the calculations which follow. Three values were estimated for each stratum: the catch of bigeye (inducting fish not retained); the retained catch of all other tunas; and the number of sets made on floating objects.

The possibility of dosing strata to fishing on floating objects, based on catch data for previous years, was investigated by computer simulation with a mathematical technique called linear programming. The strata with the greatest catches of bigeye and the smallest catches of other species during two of the three years were eliminated, one by one, until the simulated catch of bigeye was reduced to 20 percent of the actual catch. Then these strata were dosed during the third year, simulating the effects of regulations based on information on the catches during the other two years. Effort from strata which were dosed was not reassigned to other strata in one set of calculations (Scenario 1; Table 8), but was reassigned proportionally to existing effort in the other set of calculations (Scenario 2; Table 9). During the first qUalier of 1996, for example, the effects of the regulations would be as follows:

Scenario 1- reduction of the catch of bigeye from 11,503 to 5,362 metric tons and reduction of the catch of other tunas from 17,183 to 14,610 metric tons (Table 8);

Scenario 2-reduction of the catch of bigeye from 11,503 to 6,830 metric tons and increase of the catch of other tunas from 17,183 to 18,608 metric tons (Table 9). The desired effect, as noted above, was to reduce the catch of bigeye by 80 percent of what it would have been without regulation, but with Scenario 1it was reduced by only 53 percent ((1- (5,362/11,503)) x 100) of that amount and with Scenm10 2it was reduced by only 41 percent ((1- (6,830/11,503)) x 100) of that amount.

The linear program has the effect of ordering the strata by the ratio of the catch of bigeye to the retained catch of the other species. This ratio has been calculated for each stratum of (1) the two years sampled and (2) the year which was out of the sample. Each pair of such values is plotted in Figure 22. The scatter of the points demonstrates that it is not possible to predict accurately the ratio in a seasonarea stratum of one year from its value in two other years. Similarly, in Figure 23 the retained catch of the other species in one year has been plotted against the sum of the retained catch of the other species in the other two years. Again, the scatter illustrates the large variation between one year and the other two in the series. Large-scale changes in the environment, such as EI Nino events, would be likely to exacerbate this variability.

The year-to-year variability in the distribution of the ratio of bigeye catches to the retained catch of other tunas makes it difficult to manage bigeye without affecting the catches of other tunas. This is likely to remain the case until the distributions of tunas can be predicted with reference to external factors such as the movement of water masses. Recognizing this, the working group asked the staff to consider the effects of restrictions on fishing in larger areas.

Tuna tagging

An IA'ITC scientist participated in a tag-mld-release program directed at yellowfm and bigeye tuna near Hawaii, conducted by the Pelagic Fisheries Research Program at the Joint Institute of Marine and Atmospheric Research, School of Ocean and Earth Sciences and Technology, University of Hawaii at Manoa, during 1995 and 1996. Atagged yellowfin, released in November 1996, was recaptured in the eastern Pacific Ocean (EPa) in July 1997. This is only the fourth record of movement of a yellowfin from the central or western Pacific to the EPa, and the first for which the interval between release and recapture was less than 1year. Details on the locations and dates of release and recapture are listed in Table 10.

About 20,000 skipjack, plus small numbers of yellowfin and bigeye, were tagged and released near the Hawaiian Islands and elsewhere in the central Pacific Ocean during 1954-1970 by what is now the U.S. National Marine Fisheries Service. There are no published records of returns of skipjack or yellowfin from these releases recaptured at locations other than the Hawaiian Islands.


Swordfish studies

A member of the IATTC staff participated on a swordfish research cruise aboard the U.S. National Marine Fisheries Service (:'-IMFS) vessel Townsend Cromwell in the eastern Pacific Ocean, mostly between 5°N and looN in the vicinity of 140oW, from August 30 to September 29, 1997. The principal objectives of the cruise were to collect juvenile and adult swordfish with longlines, and larval and early-juvenile swordfish with zooplankton nets, for morphometric, meristic, and genetic studies, and to deternline how to catch swordfish suitable for tagging. Longlining was conducted for 17 days. Generally, 450 to 500 hooks were used on each set of the longline. Frozen squid was used for bait, and a light-stick was attached to each gangion. The line was set each evening; retrieval was initiated each morning at about 4:00 a.m., and was completed by about 10:00 a.m. The temperature, salinity, dissolved oxygen, chlorophyll, and current structure were measured at various depths. Thirty-one swordfish, seven blue marlin, four striped marlin, yellowfrn and bigeye tuna, and many sharks were caught on the longline. Morphometric data and data on reproductive activity from the blue and striped marlin and genetic data from the swordfish and bigeye were collected for investigations currently being conducted by the IATTC, in cooperation with other organizations. Also, by arrangement with the NMFS, dart tags of the National Research Institute of Far Seas Fisheries, Japan, were placed on a large number of sharks. Although identification of the organisms obtained in zooplankton tows conducted in the vicinity of the Hawaiian Islands while in transit to and from the longline fishing grounds has not yet been completed, it is known that these tows captured at least one juvenile swordfish.

Early life history studies

For many years fisheries scientists have believed that the abundance of a population of fish is determined principally during its early life history (egg, larval, and/or early-juvenile) stages. Although decades of research have provided considerable information on the populations of adult tunas, relatively little is known about the early life history stages and the factors which affect their recruitment to the exploitable stocks. These considerations motivated the IATTC to establish a research facility at Achotines Bay in the Republic of Panama for the purpose of studying the early life histories of tunas.

Achotines Bay is located on the southern coast of the Azuero Peninsula in the Los Santos province of Panama (Figure 24). The continental shelf is quite narrow at this location; the 200-m (109fathom) depth contour occurs only 6to 10 km (3 to 5nm) from shore. This provides the scientists working at the Achotines Laboratory with ready access to oceanic waters where spawning of tunas occurs during every month ofthe year. The ailliual range of sea-surface temperature in these waters is approximately 21° to 29°C (70° to 84°F). Seawater pumped from Achotines Bay is suitable for maintaining live tlmas in the laboratory. The proximity of the research station to the study area provides a low-cost alternative to a large research vessel, and improves sampling flexibility.

The Ll\TTC's early life history research program involves laboratory and field studies aimed at gaining insight into the recruitment process and the factors that affect it. Previous research on recruitment of fishes suggests that abiotic factors, such as temperature and salinity, and biological factors, such as feeding and predation, can affect recruitment. As the survival of pre-recruit fishes is probably controlled by a combination of these factors, the research program addresses the interaction between the biological system and the physical environment (IATTC Data Report 9).

Much of the early work at the Laboratory was devoted to developing methods of capturing, transferring, and maintaining live scombrids in captivity. Late-larval (late notochord flexion and post-flexion stages) and early~uvenile scombrids (approximately 8 to 35 mm standard length, SL) are captured for research purposes by nightlighting from a skiff. (Nightlighting consists of attracting fish to an underwater light at night and collecting them with a dipnet.) Yellowfin and/or bigeye tuna (lwreafter, when appropriate, referred to as Thunnus spp.); black skipjack tuna, Euthynnus lineatus; frigate and/or bullet tuna,

28 TUNA COMMISSION

Auxis thazard and/or A. rochei (hereafter, when appropriate, referred to as Auxis spp.); sierra, Scornberornorns sierra; chub mackerel, Scornber japonicus; and striped bonito, Sarda orientalis, have been captured in this manner and held in the laboratory. (Lalval and early-juvenile yellowfm and bigeye cannot be distinguished on the basis of morphological, meristic, osteological, or pigmentation characters; identification of early juveniles by electrophoretic means has been described (LS. Nat. Mar. Fish. Serv., Fish. Bull., 86 (4): 835-838). Larval and early-juvenile Auxis thaza:rd and A. rochei have been distinguished by minor differences in pigmentation, body depth, and gill raker cOlmts, but there is disagreement concerning the validity of these identifying characteristics.) Through 1995, research at the Achotines Laboratory had been focused mostly on black skipjack, Auxis spp., and sierra, the most abundant scombrids in nearshore waters offthe soutllem Azuero Peninsula. Beginning in 1996, research efforts increa.


itored to ensure that it provides enough energy to fuel high growth rates and spawning, but does not cause excess fat deposition. Abioenergetics model, combined with estimates of the growth rates of the fish in Tank 1, is being used as a guideline for detennining daily ration schedules. The infonnation on the proximate composition (protein, moisture, fat, and ash) of the food organisms and the broodstock fish (obtained from fish which occasionally died or were sacrificed) are used to adjust the model. The food organisms have included squid (Loligo spp.), anchovetas (Cetengraulis mysticetus), thread herring (Opisthonema spp.), and bigscale anchovies (Anchovia macrolepidota), and the diet is supplemented with vitamin and bile powders. Several specimens of each food taxon have been dried, homogenized, and analyzed for proximate composition by a laboratory in Aguadulce, Panama. On average, the anchovetas contain about 64 percent more calories and the thread herring about 116 percent more calories than the squid. By adjusting the quantities and proportions of squid and fish in the diet, the amount of food is kept high enough to avoid frenzied feeding activity, while not greatly exceeding the requirements for metabolism, growth, reproduction, and waste losses. The broodstock in Tank 1were fed at approximately 3to 5 percent of their body weight per day during 1997. During the year six yellowfm were removed from Tank 1to analyze their condition. The fish appeared to be in good health, and fat deposition was not excessive.

At the end of the year there were 26 yellowfin in Tank 1. Seven mortalities occurred during the year; these were due to starvation (1 fish), wall strikes (5 fish), and jumping out of the tank (l fish). The estimated lengths and weights of the captive fish at the end of the year in Tank 1averaged 117 em (46 inches) and 32 kg (70 pounds), and ranged from 105 to 132 ern (41 to 52 inches) and 29 to 45 kg (64 to 99 pounds). These estimates are based on average growth rates calculated for the fish that were sacrificed or died during the year. At the end of the year the biomass in the broodstock tank was estimated to be 0.61 kg per cubic meter, which is slightly greater than the original target stocking density of 0.50 kg per cubic meter for the broodstock population.

The yellowfin in Tank 2were held in reserve to augment the broodstock population in Tank 1, should that become necessary. The population in Tank 2 was gradually reduced during 1997, and the last four fish were sacrificed late in the year. These fish were used to produce eggs and larvae that were analyzed for direct genetic inheritance information. At the end of the year fishing effort to restock Tank 2 began.

Yellowfin spawning

The yellowfin in Tank 1spawned at nearly daily intervals during most of 1997. The water temperatures in the tank during spawning ranged from 24.40 to 29.5°C (75.9° to 85.1 oF). Spawning ceased from mid-March to mid-April, when strong upwelling occurred in the coastal waters near the Laboratory. During the upwelling period the water temperatures in Tank 1 ranged from 20.0° to 24.0°C (68.0°

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ANNUAL REPORT - Inter-American Tropical Tuna Commission · 2018-06-27 · ANNUAL REPORT OF THE INTER-AMERICAN TROPICAL TUNA COMMISSION, 1997. INTRODUCTION. The Inter-American Tropical1\ma